Femoroacetabular impingement (FAI) is a cause of tears to the acetabular labrum and damage to the front rim of the hip socket, which may, over many decades, lead to osteoarthritis of the hip. In a normal hip the ball of the ball and socket joint is perfectly spherical and it sits inside a spherical socket so that there are no mechanical conflicts with movement in any direction. Hip joints in FAI, however, are not perfectly shaped: impingement hips have a flattening (the cam or the ‘bump’) at the front of the ball, which catches on the labrum and cartilage at the front of the socket with flexion and rotation movements, eventually causing damage. See a cam shaft in action
The cam itself develops as part of skeletal growth during childhood and adolescence but does not cause any symptoms until it has caused damage to the labrum and socket. Damage is cumulative and depends on the size of the cam, the ability of the labrum and cartilage to withstand injury, and the duration and intensity of activity. Age of onset of symptoms is typically in the 30s and 40s, although it is increasingly common to see symptoms in teenagers.
Whilst early symptoms of FAI can be treated with physiotherapy and activity modification, surgery is the only way of removing the cam and correcting the mechanical abnormality. The aims of surgery include tidying-up the damaged labrum and cartilage and reshaping the femoral head so that it is spherical. Any additional prominence of the socket at the front can also be dealt with at the same time. The aim of surgery is to relieve pain and restore movement, but clearly it also improves the mechanics of the hip so that progression of damage is stopped or slowed. It also follows that surgery is most effective before the damage to the hip is too severe. Surgery for FAI has evolved rapidly over the last decade and the type of surgery depends on the location and types of bony abnormality and the patient’s age. Whilst the majority of FAI can be treated arthroscopically, it is also important to appreciate that some deformities can only be comprehensively treated with open surgery. Under treatment may lead to persisting or recurrent symptoms and the inconvenience and unpredictability of repeat surgery.
Surgery should be considered when:
- Symptoms are starting to affect day to day activities or walking
- Patients’ exercise remains affected despite reducing intensity
- Symptoms have been present at least six months and are deteriorating / not improving
- Non-surgical treatments have been ineffective
- Elite and professional athletes
Clearly the decision to operate is based on individual circumstances and careful discussion should take place between patient and their surgeon before proceeding with surgery.